The Capitals were a fairly disciplined team in the second half of the regular season, averaging just 3.4 minors and 3.0 penalty kills per game — a significant drop from the 4.2 and 3.9 they averaged in the first half of the season.

Yet those undisciplined ways returned at an inopportune time Monday during the Capitals’ 4-3 loss to the Rangers in Game 3. Washington took six minor penalties in the game and faced six penalty-killing situations. The Capitals had only two games all season — both in January — with more than six penalty kills.

“I just felt like the first two periods, all we were doing was killing,” forward Eric Fehr said Tuesday. “I don’t even remember a five-on-five shift with my line.”

The Capitals officially killed off five of the Rangers’ six power-play chances, though Rangers forward Brian Boyle’s first-period goal was practically a power-play goal, since forward Joel Ward was just leaving the penalty box when Boyle scored.

While the Capitals had some success with the penalty kill, taking that many penalties in a short span — six in the first 26:32 — stunted their momentum and wasted energy.

“It’s very hard [to keep a rhythm with so many penalties],” coach Adam Oates said, adding that he felt some of the penalty calls Monday night were “dicey.”

Washington’s offensive stars not tasked with penalty killing, particularly Alex Ovechkin and forward Mike Ribeiro, risk going cold if they’re left sitting on the bench too long, Oates noted.

“Troy [Brouwer] killed, Marty [Erat] kills, [Nicklas Backstrom] kills. Ovi’s sitting there,” Oates said. “It factors into the minutes.”

Oates even double-shifted Ovechkin on the fourth line during the second period to get him back into a groove.

When at even-strength, the Capitals played a solid game and were in a position to claim a 3-0 series lead, but that was undone by their penalty troubles.

One power-play goal has been scored in each game of the series so far, each one by the team that went on to win the game.

Discipline will be a primary focus during Game 4 tonight.

“Our PK has been great for us as of late, but if you take that many penalties, they’re bound to get good looks. They’re bound to score,” Brouwer said. “A lot of our penalties were unnecessary penalties away from our goal, which gives them an opportunity to try and score. We’ve got to clean up that aspect of our game, continue to work hard, continue to finish our checks, but do it without taking penalties.”